Lecture 8: Reproductive behaviour

Question 1

Genetic basis of sexual differentiation

Answer 1

• more info carried X

- Y function = control development of glands that produce the male sex hormones

Question 2

Genetic determination of sex

Answer 2

• M&F same until 6 weeks

- presence/absence of Y chromosome that leads to development of either M/F gonads

Question 3

Wolffian duct

Answer 3

-has capacity to develop into male reproductive system

Question 4

Mullerian duct

Answer 4

-has capacity to develop into female reproductive system

Question 5

SYR

Answer 5

• week 7
• gene of Y causes formation of gonads into testes
• absense allows gonads to develop into ovaries
• female gender is default setting until enzymatic activity

Question 6

Internal sexual differentiation male

Answer 6

XY: with testicular hormones and mullein duct inhibiting substance

• male system develops and female system dissipates
• Anti-mullerian= defeminising

Androgen=masculating hormone

Question 7

Internal sexual differentiation Female

Answer 7

XX: without testicular hormones

• ovaries dont release hormones at the stage
• lack of other hormones that cause male system to break down and Mullerian system develops

Question 8

Androgen insensitivity syndrome

Answer 8

• genetically male XY
• lack of testosterone not helping the male system to develop
• non/low functioning androgen receptors
• wolffian system retarded

Question 9

Persistent mullerian duct syndrome

Answer 9

• genetic male

- no anti-mullerian hormone not allowing female system to dissipate so both sets of gender organs are developed

Question 10

Sexual differentiation

External

Answer 10

-external sex organs develop at 8-12 weeks due to presence or absence of testosterone and anti-mullerian hormone

T= male organs
No T=female organs

Question 11

Puberty

Answer 11

• 10.5 for girls
• 11.5 for boys
• increase in release of hormones by the anterior pituitary gland
• increase in GnRH and adrenocorticotropins lead to the release of gonadotropic hormones from the gonads and adrenaline cortex (LH and FSH)
• these hormones lead to secretion of six hormones from the gonads which causes maturation of the genitals and development of secondary sex characteristics

Question 12

What happens in puberty

Answer 12

Males
-androgen levels are higher than oestrogen leading to masculisation

Females
-estrogen hormones are predominate

**people castrated before puberty dont become sexually mature unless receive replacement injections

Bi-potentiality of secondary sex characteristics remains throughout life –
 males given estrogen to treat tumour = breasts and fine facial hair
 women with androgen secretion from a tumour = beard and lowered voice

Question 13

Hormonal control of sexual behaviour

Answer 13

• Sexual behaviour of male animals (non-primate) depends on testosterone (secreted by testes)
• Female (non-primate) sexual behaviour depends on estrus cycle (increase in estradiol followed by progesterone)

Question 14

Influences of sex hormones on human behaviour

Answer 14

• Sexual initiation in females but not males is associated with menstrual cycle
• GnRH antagonist reduces sexual interest, fantasy and intercourse in young males
• Anticipation of sexual activity can increase testosterone levels in men
• Testosterone levels in women and men affects and is affected by sexual behaviour
• Behaviour can influence hormones just as hormones can influence behaviour

Question 15

Pheromones

Answer 15

*Hormones carry messages from the secreting gland to target tissue within an organism

Carry messages between animals 
     via olfaction (sniffing or tasting)
•	Vomeronasal organ → olfactory 
bulb → medial nucleus of amygdala
•	Mostly present in sweat or 
urine

Question 16

Lee-boot effect

Answer 16

The slowing and eventual cessation of estrous cycles in groups of female animals that are housed together; caused by a pheromone in the male animal’s urine.

Question 17

Coolidge effect

Answer 17

The restorative effect of introducing a new female sex partner to a male in refractory period after sexual activity; caused by a pheromone in the female animal’s urine

Question 18

Whitten effect

Answer 18

The synchronization of the menstrual or estrous cycle of a group of females, which occurs only in the presence of a pheromone in a male’s urine.

Question 19

Vandenbergh effect

Answer 19

The earlier onset of puberty seen in female animals that are housed with males; caused by a pheromone in the male’s urine.

Question 20

Bruce effect

Answer 20

Termination of pregnancy caused by the odour of a pheromone in the urine of a male other than the one that impregnated the female.

Question 21

Human pheromones?

Answer 21

• Female menstrual cycle
• Female groups – nuns, single-sex colleges (McClintock, 1971) cycles sync
• Underarm perspiration study (Russell, Switz and Thompson, 1980) donor of sweat and recipient cycled synced
• Male groups shorten cycle – armed forces
• Male and female body odour can be distinguished
• Female body odour rated as more pleasant and “sexy” during ovulatory (fertile) phase
• Pheromones or sensory signals?
• Human vomeronasal organ inactive (sparse receptors)
• Standard olfactory system may be able to detect Pheromones
• Detection of odours can be unconscious

Question 22

Sexual orientation

Prenatal hypothesis

Answer 22

Male homosexual = not masculinised or defeminized

Female homosexual= masculinised but not de-feminized

Bisexual= masculinised, not defeminized

Question 23

Support prenatal hypothesis –CAH disorder

-Androgen insensitivity syndrome

Answer 23

• females adrenal gland secretes excessive amounts of androgens
• These individuals are genetically male (XY) but have female external genitalia (no defeminising) - usually have the testes removed surgically and live as women (with treatment of female hormones in adulthood).

Question 24

Neural control of sexual behaviour Males

Answer 24

•Medial preoptic area (MPA)

• area of cell bodies just rostral to the hypothalamus
• Electrical stimulation induces copulatory behaviour/ copulation increases activity in this area/ destruction of MPA abolishes sexual behaviour
• Sexually dimorphic nucleus (SDN) - Size of structures of neurons in MPA dependent on prenatal androgen exposure
• MPA receives input from vomeronasal organ (pheromones) possibly explaining the effects of female pheromones on male rodents
• MPA controls sexual motor reflexes and receives incoming information from stimulation of the genitals

Question 25

Neural control of sexual behaviour Females

Answer 25

• Ventromedial nucleus of the hypothalamus (VMH)
• A large nucleus of the hypothalamus located near the walls of the third ventricle
• Lesions to this area stop the display of lordosis in female rodents and electrical stimulation facilitates sexual behaviour
• VMH receives input from vomeronasal organ (pheromones)
• VMH controls sexual motor reflexes via Periaqueductal Gray Matter
• Female sexual activity is activated by a priming dose of estogen followed by progesterone and injection of these hormones into the VMH stimulates sexual behaviour

Question 26

Hormonal control of maternal behaviour

Answer 26

• no evidence of organisational effect of hormones play a role
• maternal behaviour is affected by hormones but not controlled by them

Question 27

Neural control of parental behaviour: Maternal

Answer 27

• Medial preoptic area (MPA) plays most critical role
• Lesions of this area disrupted both nest building and pup care – mothers simply ignored their offspring (Numan 1974)
• Most species of mammals are cared for by mothers but a few species of rats share task of infant care

Question 28

Neural control of behaviour: Paternal

Answer 28

• Brains of these nurturing fathers show some interesting differences to nonpaternal fathers of other species
• Size of MPA shows less sexual dimorphism in
monogamous voles than promiscuous voles
• Increased Fos production when male prairie voles
were exposed to a pup
• Lesions of MPA produce severe deficits in paternal behaviour in rats